I didn't have the best of luck searching for my answer so I apologize if this is an oft-discussed topic.

I've got a 2004 SS with the 3800. I consume around a quart of oil every 5,000 miles. It's not under the car, which could be good or bad, I suppose.

My main question, is there any way to tell if an oil leak is through the piston seals versus valve seal leaking? I don't have oil in my coolant, so I don't think it's a gasket. Can I do a compression check on each cylinder to see if one has less compression? That would theoretically tell me where I have air gaps, right? Or is it more likely that this is occuring to each chamber?

Any helpful advice would be appreciated.

 

Are you supercharged or not? In 04 they had both in the SS.

I would say about a quart in 5k could be just a tiny tiny leak somewhere that it isn't noticeable. I don't think it could be a seal since you would see that in the exhaust usually.

You could get it tested, but you really might just have some failing gaskets letting it weep out very slowly

 

Sorry for not clarifying, I am naturally aspirated.

Regarding the exhaust, the fact that I have seen no smoke is putting me off in my thought process for what it could be.

I've done some pretty thorough engine bay inspections and haven't seen any build up of oil. Any recommendations for areas I should focus on? Obviously I can't check internal gaskets, but does this engine have any consistent gasket issues? With that last comment, I'm thinking about how my wife's Malibu had the bad lower intake manifold gasket.

 

Yes these cars are notorious for LIM gasket issues.

But also valve covers can leak every now and then. Are your exhaust manifolds dirty? Can you smell a tiny bit of oil being burned off?

Even the oil-pan gasket has been known to leak a tiny bit.

 

Forward manifold is clean. Obviously, it's a little harder to casually check the aft. I'll have to get myself some better angles tonight to check it out. No smells of oil burning, but maybe it's so miniscule I'm missing it.

Oil pan is very clean. I would highly doubt it's that, but I'll check it again. I've had this mystery consumption for quite a while, so I'd expect to see buildup if I'm leaking out. I'll do a little more in depth searching tonight.

Regarding the LIM, my wife's 'Bu would lose coolant instead of oil. Is it just as likely to lose oil instead of coolant? If I'm losing oil, I would see it if I did a coolant drain, right? One step further with that logic, since my cooling system has a finite capacity, isn't there a certain point where the system just couldn't take any more oil?

 

You know what could also happen? Luckily this idea of mine is a $5 and 5 minute fix.

PCV system. If it isn't venting your system properly it can throw some oil into the combustion chamber. The PCV valve should rattle when you shake it. Don't lose the o-ring for it either.

 

I changed the PCV valve about 7/8 months ago as a potential fix, it didn't slow down the consumption. I suppose I could do it again.

If I told you the intake side of my throttle body was so gunked up with black crap that it was actually making my throttle body stick shut, would that impact your assesment of this situation? Whenever the car was cold, I could feel (through the gas pedal) the plate break from the gunk. Once the car was warm it wouldn't stick anymore. I cleaned the throttle body, though it could be on it's way to gunk again.

 

Yeah that is some excessive carbon build-up. Taking the TB off and cleaning it, maybe even Seafoaming your engine can help with that.

I was experiencing that TB "stick" also, so I decided to clean the TB (and replace the gasket).

 

Both exhaust manifolds are clean, nothing burning on them.

On the forward facing part of the engine, between the head and the upper intake there appeared to be a lot of wet debris and sand and stuff. So if my terminology is correct, this debris was sitting directly on the lower intake. To the touch, it was dirty and dark, possibly oil. See picture below for my awesome MS Paint skills. The red area is where the "wet" areas are.

Is that normally a clean area? It's a recessed area, so any moisture from the road could conceivably end up in this location. With a little more time tomorrow I'm going to clean that area really well then monitor it more closely to see if I'm leaking oil into there. It didn't hardly seem like there was a couple quarts worth of oil in that area, but is it conceivable that that area would be hot enough to burn off that oil over time?

 

I'm rebumping an old thread, but it's mainly just to put an update on here so if anyone in the future searches for it they'll see it.

My Monte had eventually got to the point where it was consuming about a quart of oil every 3,500 miles. As I was driving down the road this past winter my LIM gaskets decided to completely go. Since I changed those I've now put 5,500 miles on my current oil and the oil mark on the dipstick has not budged even a little. I had no oil in my coolant when I did the change and I never had a leak under the car or out the exhaust. It seems that my LIM's were maybe just leaking by so very slightly that I never noticed the oil, but since I made the change I've been consuming no oil. I'll call that a win.